309

LONG-TERM TRENDS OF PERSISTENT ORGANOCHLORINE POLLUTANTS,OCCUPANCY, AND REPRODUCTIVE SUCCESS IN PEREGRINE FALCONS (FALCO

PEREGRINUS TUNDRIUS) BREEDING NEAR RANKIN INLET, NUNAVUT, CANADA

ALASTAIR FRANKE1, MIKE SETTERINGTON2*, GORDON COURT3, AND DETLEF BIRKHOLZ4

1Canadian Circumpolar Institute, University of Alberta, 1-42 Pembina Hall, Edmonton, Alberta T6G 2H8, Canada. E-mail: Alastair.Franke@ales.ualberta.ca

2Department of Environment, Government of Nunavut, P.O. Box 120, Arviat, Nunavut X0C 0E0, Canada

*Current address: Environmental Dynamics Incorporated, 3-478 Range Road, Whitehorse, Yukon Y1A 3A2, Canada

3Alberta Fish and Wildlife Division, 9920-108 Street, Edmonton, Alberta T5K 2M4, Canada

4ALS Laboratory Group, 5424 – 97 Street, Edmonton, Alberta T6E 5C1, Canada

ABSTRACT.—The historical decline of the Peregrine Falcon (Falco peregrinus) in North Americawas attributed mainly to reproductive failure associated with persistent organochlorine pollutants,in particular DDT (dichloro-diphenyl-trichloroethane). It is generally assumed that decliningtrends in pesticide loads will be accompanied by a corresponding increase in reproduction. In thisstudy, we concurrently measured occupancy, reproductive performance, and pesticide loads ofbreeding-aged adults on territory near Rankin Inlet, Nunavut, from 1982 to 2009. Our findingsindicate that reproductive success of Peregrine Falcons in our study population declined despiteconcomitant reductions in pesticide loads, and that on average, approximately three fewer terri-tories were occupied annually from 2002 to 2009 than were occupied from 1982 to 1989. In addi-tion, the average number of young to reach banding age annually from 2002 to 2009 wasapproximately half the number banded annually from 1982 to 1989. These results indicate that inrecent years fewer pairs have attempted to breed; in addition, those that did breed successfullyraised fewer young to banding age. In general, the pesticides examined in this study cannot mech-anistically explain either the reduction in occupancy or the decline in reproductive performance.We suggest that the proximate effects of local weather patterns—ultimately associated, eitherdirectly or indirectly, with overall climate change—have the greatest potential to explain thealtered demographic features of the Rankin Inlet population. Reproduced with the permission ofthe Arctic Institute of North America from Arctic (2010) 63(4):442–450.

FRANKE, A., M. SETTERINGTON, G. COURT, AND D. BIRKHOLZ. 2011. Long-term trends of persistentorganochlorine pollutants, occupancy and reproductive success in Peregrine Falcons (Falco pere-grinus tundrius) breeding near Rankin Inlet, Nunavut, Canada. Reproduced, pages 309–322 inR. T. Watson, T. J. Cade, M. Fuller, G. Hunt, and E. Potapov (Eds.). Gyrfalcons and Ptarmigan in

WIDESPREAD DECLINE OF THE PEREGRINE FAL-CON (Falco peregrinus) in North America wasattributed to reproductive failure (Peakall1976, Cade et al. 1988) associated with theubiquitous use of persistent organochlorinepollutants, in particular DDT (dichloro-diphenyl-trichloroethane) (Hickey 1969, Fyfeet al. 1976, Cade et al. 1988, Ratcliffe 1993,Cade and Burnham 2003). Despite bans on theuse of DDT imposed in Canada in 1969 and inthe United States in 1972 (Kiff 1988), thePeregrine Falcon of continental North America(F. p. anatum) was extirpated over its rangeeast of the Rocky Mountains and south of theboreal forest by 1975 (Fyfe et al. 1976). How-ever, the species has shown considerablerecovery over the last two decades (Ambroseet al. 1988, Rowell et al. 2003, Cade and Burn-ham 2003, Banasch and Holroyd 2004), in partdue to the release of captive-bred birds. In2006, the Committee on the Status of Endan-gered Wildlife in Canada (COSEWIC) down-graded the threat level for the continentalsub-species F. p. anatum from “Threatened” to“Special Concern” (COSEWIC 2006), and thePeregrine Falcon, F. peregrinus, was removedfrom the United States list of endangered ani-mals in 1999.

The strong recovery of Peregrine Falcon pop-ulations in North America is assumed to havebeen fueled by two main factors: captivebreeding with re-introduction and, just asimportant, a decline in persistent organochlo-rine residues in Peregrine Falcons and theirprey species. Remarkably, there exist relativelyfew studies of the toxicological status of NorthAmerican Peregrine populations during thisrecovery era. Court (1993) assessed the toxi-cology of Peregrine Falcons (F. p. anatum)breeding in Alberta, Canada between 1968 and

1992, while Court et al. (1990) and Johnstoneet al. (1996) reported on the toxicology of theRankin Inlet population from 1982 to 1986 and1990 to 1994, respectively. Jarman et al.(1994) reported on organochlorine compoundsin the plasma of Peregrine Falcons nesting inGreenland. More recently, Henny et al. (1996,2009) reported on trends of organochlorinecontaminant levels in migrant Peregrine Fal-cons captured on Padre Island, Texas, andVorkamp et al. (2009) summarized long-termtrends in residues found in nesting birds inGreenland.

The present study has two primary objectives.The first was to summarize the changes inblood plasma concentration of dichloro-diphenyl-dichloro-ethylene (DDE), a metabo-lite of DDT; polychlorinated biphenyls(PCBs); and dieldrin in adult Peregrine Fal-cons captured on territory at Rankin Inlet from1982 to 2006. The second was to report onannual occupancy and nestling productivity ofthese birds from 1982 to 2009. We also presenttrends in average summer temperature and pat-terns of precipitation experienced at RankinInlet over the same period.

STUDYAREA

The study population of Peregrine Falcons isencompassed within a 455 km2 study area(Figure 1) near the hamlet of Rankin Inlet,Nunavut, Canada. At peak density, breedingPeregrine Falcons at Rankin Inlet included 29territorial pairs, or one pair per 15 km2, whichis the highest density recorded for the speciesin the tundra biome and among the highest inthe world. Though Rankin Inlet (62°49'N,92°05'W) is a relatively southern location forPeregrine Falcons in the Canadian Arctic,

310

– FRANKE ET AL. –

a Changing World, Volume II. The Peregrine Fund, Boise, Idaho, USA. http://dx.doi.org/10.4080/gpcw.2011.0309

Key words: Peregrine, Falco peregrinus, Arctic, Nunavut, organochlorine, productivity, occu-pancy, weather, temperature, precipitation, climate change.

311

– REPRODUCTIVE SUCCESS OF PEREGRINE FALCONS –

environmental conditions are as severe as, ormore severe than, any encountered in the rangeof the species. Passerines and small mammalscomprise the bulk of the diet, and lemmingconsumption increases significantly duringpeak abundance (Court et al. l988a, b, Bradleyand Oliphant 1991). Terminology used indescribing nesting activities of Peregrine Fal-cons and a general description of vegetation,climate, and geology of the study area arereported elsewhere (Court 1986, Court et al.l988a, b, 1989).

METHODS

Occupancy and Reproductive Success.—Accurate determination of site occupancy eachbreeding season was impossible to achievewith a single, short-term survey, particularly ifthe survey was conducted later in the breedingseason (e.g., at a period of time typically asso-ciated with brooding or chick rearing). For thisreason, from 1982 to 2008, a full census of theentire study area was conducted a minimum oftwice annually. Beginning in May of each year,

as Peregrine Falcons arrived from their winter-ing grounds, territories were surveyed by snowmachine to determine the presence or absenceof territorial, breeding-aged, adults. All unoc-cupied sites were checked until occupancy byPeregrine Falcons was confirmed, or until thebreeding season was sufficiently advanced toconclude that the site was vacant.

In cases where sites were occupied by individ-uals previously fitted with unique alphanu-meric color-coded leg bands, bands were readusing a Questar Field Model telescope. If ter-ritories were occupied by unmarked individu-als, effort was made to trap and mark thesebirds with an alphanumeric color band on oneleg and a US Fish and Wildlife band on theother. In addition, we measured unflattenedwing chord, body weight, tail length, and tar-sus width and length for each bird andrecorded sharpness of keel, a subjective meas-ure of body condition.

After breakup of the sea ice, territories weresurveyed by boat to determine occupancy and

Figure 1. Map of Canada showing the location of the Rankin Inlet, Nunavut, study area (enlarged ininset).

reproduction at each site; inland sites wereaccessed by all-terrain vehicle for the samepurpose. During summer, banded adult Pere-grine Falcons were identified either by trap-ping or visually by telescope. Unmarkedindividuals were trapped and banded whenpossible. Once nestlings reached a minimumof 20 days of age (approximately July 25), theytoo were banded with an alphanumeric colorband on one leg and a US Fish and Wildlifeband on the other. Only young that survivedbeyond 20 days and were banded wereincluded in the annual nestling census. Of the36 known territories distributed throughout thestudy area, 22 were surveyed annually from1982 to 2009. To ensure that data were notbiased by inconsistent survey effort, our esti-mates of site occupancy and productivity werecalculated using only the 22 sites surveyedannually in both spring and summer. The years2000 and 2001 were excluded from this analy-sis because in 2000, surveys were conductedonly in summer, and in 2001, no survey wasconducted at all.

Organochlorine Residues.—We used singlefactor ANOVA and Tukey post-hoc tests in thestatistical package R to undertake multiplecomparisons of means to compare occupancyand total number of young produced, as wellas reproductive success across three distinctperiods of time (1982–89, 1990–99, and 2002–09), which allowed us to approximate decadaltrends. Productivity (the number of young perterritorial pair per year) is an alternative meas-ure of reproductive success that takes intoaccount the number of breeding pairs presenton a territory in a given year, regardless ofwhether the breeding attempt was successful.We therefore calculated productivity in aneffort to ensure that changes in the number ofyoung were not related simply to changes inthe number of pairs that attempted to breed inany given year.

Between 1982 and 2005, 54 adult male and 93adult female Peregrine Falcons were captured;approximately 2 ml whole blood was collected

from the ulnar vein of each bird using a 23-gauge needle and a 3-cc syringe. Some individ-uals were trapped in multiple years, resulting ina total of 197 blood samples, 61 for males and136 for females, each of which was consideredto be an independent observation. Sampleswere stored in heparin and centrifuged to sep-arate red cells from plasma. Samples weresealed and stored frozen at 0°F (–17°C) untilanalysis. All toxicological analyses for samplescollected for the periods 1982 – 1986 and 1990– 1996 were conducted at the Health of Ani-mals Laboratory, Food Animal ChemicalResidues Section, Agriculture and Agri-FoodCanada, in Saskatoon. Preparation of samples,initial assay, and confirmatory gas chromatog-raphy-mass spectrometry analyses followed themethods of Won and Turle (1987) and Burse etal. (1983), as used by Court et al. (1990). Thequality assurance program run by the Health ofAnimals Laboratory permitted comparisonsbetween samples collected from 1991 to 1994(Johnstone et al. 1996) and earlier samples col-lected by Court et al. (1990). Pesticide refer-ence standards used for quantification werevalidated according to the Health of AnimalsLaboratory QA protocol. All remaining sam-ples were analyzed commercially using USEnvironmental Protection Agency (EPA)Method 8081b (US-EPA 2007a).

Samples were extracted as reported above;however, cleanup of the extracts was per-formed using a 12 g Florisil column. Thecleanup extract was analyzed using high reso-lution gas chromatography/electron capturedetection. Two columns were used: a 30 m x0.25 mm I.D. DB-5 and a 30 m x 0.25 mm I.D.DB-1701. We used hydrogen carrier gas toillicit maximum peak resolution, and per-formed dual column confirmation by compar-ing responses for the two different columns.Analyses for PCBs were performed using Aro-clor matching (Method 8082A, US-EPA2007b). For biological samples, it is generallyrecognized that this procedure will returnhigher detection rates than congener-specificanalyses (Burse et al. 1990).

312

– FRANKE ET AL. –

313

– REPRODUCTIVE SUCCESS OF PEREGRINE FALCONS –

Data were log-transformed (zero values wereset to 0.0005 mg/kg, the stated minimumdetection limit) and are reported as geometricmean mg/kg wet weight. We used single factorANOVA and Tukey post-hoc tests in the statis-tical package R to undertake multiple compar-isons of means to compare blood plasmaresidues (4,4'-DDE, ΣPCB, and dieldrin)across three distinct periods of time (1982–86,1990–98 and 2004–06).

Weather.—We used Environment Canadaweather data collected at the Rankin Inlet air-port to calculate average summer temperature(°C), total summer precipitation (mm), andmonthly precipitation for June through Augustfor 1982—2009. We used proc AUTOREG inSAS v.9 (SAS Institute 2004) to regress aver-age summer temperature and total precipitationon time, correcting for temporal auto-correla-tion (and thus dependence) among the residu-als (autoregressive error regression). In

addition, we calculated the deviation inmonthly precipitation from the long-term meanfor each month from 1982 to 2009.

RESULTS

Occupancy and Reproductive Success.—Onaverage, 17.42 ± 1.96 of the 22 sites thatreceived consistent survey effort from 1982 to2009 were occupied annually by a breeding-aged pair of Peregrine Falcons and producedan average of 20.27 ± 11.55 young annually,resulting in an average of 1.15 ± 0.62 nestlingsper occupied territory per year (Figure 2, Table1). The range of natural variation across allyears was 14–21 for occupancy, 0–50 for totalproduction, and 0.0–2.38 for productivity (Fig-ure 2, Table 1).

Multiple comparisons of occupancy and totalproduction among time periods indicated a sig-nificant decline in both the number of territo-

Figure 2. Long-term trends in annual number of territorial pairs and number of young to reach bandingage each year for 22 sites in the Rankin Inlet study area monitored from 1982 to 2009.

rial pairs (P < 0.001) and the number of youngproduced (P < 0.01). There was no difference(P = 0.28) in the number of occupied territorieswhen comparing the 1980s (mean = 18.88 ±1.55) and the 1990s (mean = 17.80 ± 1.48).However, fewer territories were occupied inthe 2000s (mean = 15.50 ± 1.31) than in the1980s (mean = 18.88 ± 1.55, P < 0.001) andthe 1990s (mean = 17.80 ± 1.48, P < 0.01).

For total production, a comparison among timeperiods indicates there was no difference (P =0.77) between the 1990s (mean = 17.40 ±9.26) and the 2000s (mean = 14.25 ± 9.00).However, a significant decline is evident incomparisons between the 1980s (mean = 29.88± 11.23) and both the 1990s (mean = 17.40 ±9.26, P < 0.05) and the 2000s (mean = 14.25 ±9.00, P = 0.10).

Despite our correction for the number of terri-tories occupied each year, the decline in repro-ductive success as estimated by productivityremained consistent with the decline observedfor total production. We found no difference (P= 0.99) between estimates of productivityobserved in the 2000s (mean = 0.94 ± 0.64)and those observed in the 1990s (mean = 0.97± 0.51). Nevertheless, significant declines inproductivity were apparent when we comparedthe 1980s (mean = 1.59 ± 0.58) to the 1990s(mean = 0.97 ± 0.51, P < 0.10) and the 2000s(mean = 0.94 ± 0.64, P < 0.10).

Organochlorine Residues.—Results for bothsexes combined (Table 2) indicate that plasmaDDE levels in adult Peregrine Falcons breed-ing in Rankin Inlet were significantly higher inthe 1980s (geometric mean = 0.76 mg/kg) thanin the 1990s (0.27 mg/kg, P < 0.001) and the2000s (0.12 mg/kg, P < 0.001). However, therewas no difference in the geometric means forplasma DDE levels recorded in the 1990s andthe 2000s (P = 0.359).

For adult males, plasma DDE levels were sig-nificantly higher in the 1980s (geometric mean= 0.93 mg/kg) than in the 1990s (geometricmean = 0.18 mg/kg, P < 0.001) and the 2000s(geometric mean = 0.05 mg/kg, P < 0.001).However, there was no difference in the geo-metric means for plasma DDE levels recordedin the 1990s and 2000s (P = 0.334). Femalesalso had a significant decline in plasma DDElevels from the 1980s (geometric mean = 0.70mg/kg) to the 1990s (geometric mean = 0.31mg/kg, P = 0.02); however, the declinesobserved in the 2000s were not statisticallysignificant compared to the 1980s (P = 0.11) orthe 1990s (P = 0.95).

For both sexes combined, PCB residuesdeclined significantly from the 1980s (0.64mg/kg) to the 1990s (0.11 mg/kg, P < 0.001;Table 3), but there was no significant differ-ence between the 1980s (0.64 mg/kg) and the2000s (0.32 mg/kg, P = 0.39), or between the

314

– FRANKE ET AL. –

Table 1. Summary data (mean ± SD) for annual occupancy at 22 sites monitored for territorial adults,total production (number of young banded each year), and productivity (number of young peroccupied territory) of Peregrine Falcons breeding near Rankin Inlet, Nunavut, from 1982 to 2009.

Occupancy Production Productivity

Mean ± SD 1982–2009 17.42 ± 1.96 20.27 ± 11.55 1.15 ± 0.621982–1989 18.88 ± 1.55ab* 29.88 ± 11.23a 1.59 ± 0.58a

1990–1999 17.80 ± 1.48abc 17.40 ± 9.26b 0.97 ± 0.51b

2002–2009 15.50 ± 1.31c 14.25 ± 9.00bc 0.94 ± 0.64bc

Range1982–1989 16–21 14–50 0.7–2.381990–1999 16–20 2–31 0.8–1.742002–2009 14–18 0–31 0.0–2.21

* Means in the same column that share a superscript letter are not significantly different.

315

– REPRODUCTIVE SUCCESS OF PEREGRINE FALCONS –

Table 2. DDE (geometric mean and maximum levels) in blood plasma of adult Peregrine Falconscaptured on territory in Rankin Inlet, Nunavut, 1982 – 2006.

Both Sexes Females Males

Time Period

1982-86 0.76a* 8.19 75 0.70a 6.56 55 0.93a 8.19 20

1990-98 0.27b 4.45 97 0.31b 4.45 66 0.18b 1.95 31

2004-06 0.12bc 5.40 25 0.23ab 5.40 16 0.05bc 0.33 9

* Means in the same column that share a superscript letter are not significantly different.

Table 3. ΣPCB (geometric mean and maximum levels) in blood plasma of adult Peregrine Falconscaptured on territory in Rankin Inlet, Nunavut, 1982–2006.

Both Sexes Females Males

Time Period

1982–86 0.64a* 3.84 70 0.66a 3.84 53 0.58a 2.55 17

1990–98 0.11b 13.86 97 0.40a 13.86 66 0.01b 3.27 31

2004–06 0.32a 3.50 25 0.57a 2.40 16 0.11ca 2.80 9

* Means in the same column that share a superscript letter are not significantly different.

Geo

met

ric

mea

n (

mg

/kg

)

Max

imu

m le

vel

(mg

/kg

)

N Geo

met

ric

mea

n (

mg

/kg

)

Max

imu

m le

vel

(mg

/kg

)

N Geo

met

ric

mea

n (

mg

/kg

)

Max

imu

m le

vel

(mg

/kg

)

N

Geo

met

ric

mea

n (

mg

/kg

)

Max

imu

m le

vel

(mg

/kg

)

N Geo

met

ric

mea

n (

mg

/kg

)

Max

imu

m le

vel

(mg

/kg

)

N Geo

met

ric

mea

n (

mg

/kg

)

Max

imu

m le

vel

(mg

/kg

)

NTable 4. Dieldrin (geometric mean and maximum levels) in blood plasma of adult Peregrine Falconscaptured on territory in Rankin Inlet, Nunavut, 1982–2006.

Both Sexes Females Males

Time Period

1982–86 0.07a* 0.30 72 0.07a 0.27 54 0.08a 0.30 18

1990–98 0.0b 0.37 97 0.01b 0.37 66 <0.01b 0.30 31

2004–06 0.0bc 0.10 25 0.01bc 0.1 16 <0.01bc 0.08 9

* Means in the same column that share a superscript letter are not significantly different.

Geo

met

ric

mea

n (

mg

/kg

)

Max

imu

m le

vel

(mg

/kg

)

N Geo

met

ric

mea

n (

mg

/kg

)

Max

imu

m le

vel

(mg

/kg

)

N Geo

met

ric

mea

n (

mg

/kg

)

Max

imu

m le

vel

(mg

/kg

)

N

1990s (0.11 mg/kg) and the 2000s (0.32mg/kg, P = 0.15). Taking sex into account, wefound that although both sexes experiencedreduced ΣPCB burden between the 1980s and1990s, only males experienced a significantreduction (from 0.58 mg/kg to 0.01 mg/kg, P< 0.001), while that in females was not statis-tically significant (from 0.66 mg/kg to 0.40mg/kg, P = 0.24). Whether considered togetheror separately, male and female Peregrine Fal-cons captured on territory at Rankin Inlet in the2000s showed higher levels of PCBs (males:0.11 mg/kg; females: 0.57 mg/kg) than thecohort captured during the 1990s (males: 0.01mg/kg; females: 0.40 mg/kg).

Appreciable levels of dieldrin were recorded insamples of blood plasma collected from adultsof both sexes from 1982 to 1986 (Table 4). Thegeometric means recorded during this periodwere 0.07 mg/kg for females and 0.08 mg/kg formales, and maximum levels were 0.27 mg/kg forfemales and 0.30 mg/kg for males. Althoughmaximum levels recorded in the population inthe 1990s remained the same or increasedregardless of sex, the geometric means for bothsexes declined significantly from those recordedfrom 1982 to 1986 (Table 4).

The geometric means for both sexes decreasedno further in the 2000s from values recorded inthe previous time period (1990–98); however,substantial declines were evident in the maxi-mum values recorded in the population. Overthe course of the study, maximum dieldrin lev-els decreased to about one-third of their previ-ous levels in both females (from 0.27 mg/kg inthe 1980s to 0.10 mg/kg in the 2000s), andmales (from 0.30 mg/kg to 0.08 mg/kg).

Weather.—The average summer temperaturemeasured at Rankin Inlet increased by approx-imately 1.5˚C (slope: 0.065 ± 0.02 SE, P =0.008; R2 = 0.23) from 1982 to 2009 (Figure3). Although we found a declining trend (slope= –1.30) in total precipitation for the sameperiod, it was not significantly different fromzero (P = 0.19). Similarly, deviations calcu-

lated for each month from the averages calcu-lated for June (slope = –0.81), July (slope =0.33), and August (–0.34) from 1982 to 2009were not significantly different from zero.

DISCUSSION

Pollutant status and reproductive dysfunctionin Peregrine Falcons are well documented bothfor populations in North America in general(Berger et al. 1970; Peakall and Kiff 1988;Peakall et al. 1990) and in the Rankin Inletstudy area specifically (Court et al. 1990;Johnstone et al. 1996). Of the contaminantsmeasured here, only DDE is known to havebeen associated with population declines (fromeggshell thinning) in North American Pere-grine Falcon populations, and although theeffects of dieldrin were reportedly absent inNorth American Peregrine Falcons (Rise-brough and Peakall 1988), this contaminantwas considered important in the British Isles(Nisbet 1988). The effects of PCBs on Pere-grines, if any, remain unknown, but at least it

316

– FRANKE ET AL. –

Figure 3. Average summer temperature(average monthly temperature from June toAugust, °C) at Rankin Inlet, Nunavut, Canadafrom 1982 to 2008. Line represents the estimatedlinear trend (slope: 0.065 ± 0.02 SE, p = 0.008,R2 = 0.23). The regression was performed withproc AUTOREG in SAS v.9 (SAS Institute 2004),correcting for temporal auto-correlation, and thusdependence, among the residuals(autoregressive error regression).

is well established that neither PCBs nor diel-drin contributes to eggshell thinning.

Although this analysis showed that some indi-viduals within the Rankin Inlet populationwere as contaminated in recent years as theirancestors were more than 25 years ago, overallpopulation-level organochlorine residues inPeregrine Falcons have shown a significantdecline over the last three decades. Further-more, levels recorded throughout the studyperiod, and in particular those recorded morerecently, are significantly below levels (1.8–2.4 ppm in serum) known to cause problems ineggshells (Peakall and Kiff 1988; Court et al.1990). We believe that Peregrine Falcons thatbreed near Rankin Inlet no longer face a directthreat from the pollutants investigated in thisstudy, and in this regard, there is good reasonto be optimistic about the future of PeregrineFalcons breeding at Rankin Inlet. Similartrends have been noted previously by otherauthors (Jarman et al. 1994; Henny et al. 1996,2009; Ambrose et al. 2000; Clark et al. 2009)investigating pollutant levels in Peregrine Fal-cons in other jurisdictions, and we suggest thatthis trend most likely applies to other Canadianpopulations.

It is generally assumed that declining trends inpesticide loads will be accompanied by a cor-responding increase in productivity. We there-fore measured occupancy, reproductiveperformance, and pesticide loads concurrently.However, our findings indicated that reproduc-tive success of Peregrine Falcons in our studypopulation declined despite concomitantreductions in pesticide loads. On average,approximately three fewer territories wereoccupied annually from 2002 to 2009 thanwere occupied from 1982 to 1989. The overalldecline in reproductive success can likely beexplained in part by the presence of fewerpairs attempting to breed each year. However,it is important to note that productivity, whichaccounts for the number of occupied territo-ries, also declined significantly. Consideredtogether, these results indicate that in recent

years fewer pairs have attempted to breed, andin addition, those that were successful inbreeding raised fewer young to banding age (≥20 days of age). In general, the pesticidesexamined in this study cannot mechanisticallyexplain either the reduction in occupancy orthe decline in reproductive performance.

Although the mechanism or mechanisms (e.g.,disease, predation) associated with the reporteddeclines are unclear, the proximate effects oflocal weather patterns—ultimately associated,either directly or indirectly, with overall cli-mate change—may be noteworthy in regard toexplaining the altered demographic featuresevident in the Rankin Inlet population. We sug-gest that this factor is particularly importantgiven the documented rise in average summertemperature recorded in Rankin Inlet over thecourse of this study. Although the patterns inprecipitation examined here indicate that therewas no significant change in either the amountof rain and snow or the manner in which totalprecipitation was distributed through the sum-mer months from 1982 to 2009, it is interestingto note that the slope calculated for averagesummer precipitation was negative, as wereslopes for the deviations in June and Augustprecipitation each year relative to mean Juneand August precipitation for all years of thestudy. Conversely, a positive slope was calcu-lated for the deviation in July precipitationeach year relative to mean July precipitationfor all years of the study. It is thus feasible thatin recent years both June and August may havebecome drier, while July may have becomewetter. Increased precipitation in the month ofJuly, even if associated with reduced precipi-tation in June and August, could easily resultin widespread loss of broods, as nestlings typ-ically hatch around July 11 and remain partic-ularly vulnerable to the direct effects of coldand wet conditions until at least 21 days of age.Recently, motion-sensitive cameras deployedin our study area have documented severalcases of nest flooding (e.g., Figure 4) and haveshown that otherwise healthy broods of youngcan perish in as few as two hours after direct

317

– REPRODUCTIVE SUCCESS OF PEREGRINE FALCONS –

exposure to cold, wet conditions. In thesecases, photographic evidence indicated thatweather-killed young were either fed to sib-lings or consumed or cached by the parents. Inother cases where cameras were not present,but the presence of healthy nestlings had beenconfirmed immediately prior to an extendedperiod of inclement weather, it was not unusualfor follow-up monitoring of the same sitessoon after the poor-weather period to docu-ment a reduction in brood size or a totalabsence of nestlings. At sites where collectionof dead young was possible immediately afterextended periods of rainfall, young were oftenfound huddled together, and on occasion,examination of the carcasses revealed thatnestlings had died prior to passage of foodfrom the crop into the proventriculus (i.e., theyhad not starved).

Alternatively, poor weather may indirectlyinfluence annual reproductive success of Pere-grine Falcons in a “bottom-up” manner viaavailability of food resources. Repeated sitevisits revealed that in some cases, nestlingsthat had been initially spared from the directeffects of poor weather (by either parental careor advanced feather growth) later died as aresult of poor body condition. In theseinstances, we believe that the abundance of

prey species (primarily juvenile ground-nest-ing passerines) was reduced by adverseweather conditions to levels at which adultPeregrine Falcons were not able to provisionyoung adequately. In recent years, the car-casses of several nestlings that showed poorrates of growth or sudden declines in bodyweight at some point during rearing were col-lected, and post-mortem examination clearlyindicated that these young had been severelyfood-limited prior to their deaths. In severalcases, all nestlings within a brood experiencedsignificant weight loss (50–160 g each) duringperiods when the feeding rate decreased from6–7 prey items per day to 1–2 per day. Broodsize was routinely reduced in these cases.

The results reported here emphasize howimportant it is for wildlife agencies to continuemonitoring reproductive success of PeregrineFalcons and encourage routine residue scans intheir tissues to detect any sharp changes ineither hatching success or chemical residuesover time. In addition, declining levels oforganochlorine residues found in Peregrine tis-sue leave little room for complacency.Although there are global initiatives in place toeliminate the manufacture and use of many ofthe most environmentally damaging com-pounds, strong lobbies exist that aim to resur-rect chemicals like DDT as a short-termmeasure to control malaria and other insect-borne diseases in developing nations (Raloff2000). As virtually all the Peregrine Falconsfrom northern Canada overwinter in Mexico,Central America, and South America, anymove to resume DDT use on a large scale willbe detrimental to these birds.

Finally, it is important to note that our com-ments with regard to the observed downwardtrends in occupancy and reproductive successare limited to Peregrine Falcons breeding atRankin Inlet. Such trends may exist at broaderscales, but larger patterns can be clarified onlyby incorporating additional, geographicallydistinct areas into the study.

318

– FRANKE ET AL. –

Figure 4. A soaked adult female PeregrineFalcon breeding near Rankin Inlet, Nunavut,stands beside a clutch of almost entirelysubmerged eggs.

ACKNOWLEDGMENTS

This research was funded by ArcticNet, theNunavut Wildlife Management Board, and theDepartment of Environment, Government ofNunavut. We thank Andy Aliyak, PoiseyAlogut, Vincent L’Herault, Alex Anctil, andHilde Johansen for their contributions to field-work, and Mark Bradley, Tom Duncan, RobinJohnstone, and Dave Abernethy, who con-tributed data used in the analysis. VincentL’Herault produced the map of the study area.Jean-Francois Therrien provided precipitationsummaries, and Sebastien Descamps providedthe temperature summary. We are extremelygrateful for the help and support that wereceived from personnel of the Department ofEnvironment, especially Mitch Campbell,Raymond Mercer, David Oolooyuk, DarrenConroy, Johanne Coutu-Autut, and Peter Kat-tegatsiak. We thank the members of theKangiqliniq Hunters and Trappers Organiza-tion for their approval and ongoing support forthis research. We are also very grateful to MikeShouldice and Dorothy Tootoo from theNunavut Arctic College and to the people ofRankin Inlet. We also wish to acknowledge thecontribution of three anonymous reviewers,whose comments resulted in a much-improvedmanuscript.

LITERATURE CITED

AMBROSE, R. E., R. J. RITCHIE, C. M. WHITE,P. F. SCHEMPF, T. SWEM, AND R. DITTRICK.1988. Changes in the status of the Pere-grine Falcon populations in Alaska. Pages73–82 in T. J. Cade, J. H. Enderson, C. G.Thelander, and C. M. White (Eds.). Pere-grine Falcon Populations: Their Manage-ment and Recovery. The Peregrine Fund,Boise, Idaho, USA.

AMBROSE, R. E., A. MATZ, T. SWEM, AND P.BENTE. 2000. Environmental contaminantsin American and Arctic Peregrine Falconeggs in Alaska, 1979–95. US Fish andWildlife Service, Northern Alaska Ecolog-ical Services, Fairbanks, Alaska, USA.

BANASCH, U., AND G. HOLROYD. 2004. The1995 Peregrine Falcon survey in Canada.Occasional Paper no. 110. CanadianWildlife Service, Environment Canada.Ottawa, Canada.

BRADLEY, M., AND L. W. OLIPHANT. 1991. Thediet of Peregrine Falcons in Rankin Inlet,Northwest Territories: An unusually highproportion of mammalian prey. Condor93:193–197.

BERGER, D. D., D. W. ANDERSON, J. D.WEAVER, AND R. W. RISEBROUGH. 1970.Shell thinning in eggs of Ungava Pere-grines. Canadian Field-Naturalist 84:265–267.

BURSE, V. W., L. L. NEEDHAM, M. P. KORVER,C. R. LAPZERA, JR., AND D. D. BAYSE. 1983.Gas-liquid chromatographic determinationof polychlorinated biphenyls and a selectednumber of chlorinated hydrocarbons inserum. Journal of the Association of Offi-cial Analytical Chemists 66:32–39.

BURSE, V. W., D. F. GROCE, M. P. KORVER, P.C. MCCLURE, S. L. HEAD, L. L. NEEDHAM,C. R. LAPEZA, JR., AND A. L. SMREK. 1990.Use of reference pools to compare the qual-itative and quantitative determination ofpolychlorinated biphenyls by packed andcapillary gas chromatography with electroncapture detection. Part 1. Serum. Analyst115:243–251.

CADE, T. J., AND W. BURNHAM. 2003. Return ofthe Peregrine: A North American Saga ofTeamwork and Tenacity. The PeregrineFund, Boise, Idaho, USA.

CADE, T. J., J. H. ENDERSON, C. G. THELANDER,AND C. M. WHITE. 1988. Peregrine FalconPopulations: Their Management andRecovery. The Peregrine Fund, Boise,Idaho, USA.

CLARK, K. E., Y. ZHAO, AND C. M. KANE.2009. Organochlorine pesticides, PCBs,dioxins, and metals in postterm PeregrineFalcon (Falco peregrinus) eggs from theMid-Atlantic states, 1993–1999. Archivesof Environmental Contamination and Tox-icology 57:174–184.

319

– REPRODUCTIVE SUCCESS OF PEREGRINE FALCONS –

COSEWIC (COMMITTEE ON THE STATUS OF

ENDANGERED WILDLIFE IN CANADA). 2006.Canadian Species at Risk.

COURT, G. S. 1986. Some aspects of the repro-ductive biology of Tundra Peregrine Fal-cons. M.Sc. thesis, University of Alberta,Edmonton, Alberta, Canada.

COURT, G. S. 1993. A toxicological assessmentof the American Peregrine Falcon (Falcoperegrinus anatum) breeding in Alberta,Canada, 1968 to 1992. Occasional Paperno. 10. Department of Environmental Pro-tection, Fish and Wildlife Division, Gov-ernment of Alberta, Edmonton, Canada.

COURT, G. S., C. C. GATES, AND D. A. BOAG.1988a. Natural history of the Peregrine Fal-con in the Keewatin District of the North-west Territories. Arctic 41:17–30.

COURT, G. S., D. M. BRADLEY, C. C. GATES,AND D. A. BOAG. 1988b. The populationbiology of Peregrine Falcons in the Kee-watin District of the Northwest Territories,Canada. Pages 729–739 in T. J. Cade, J. H.Enderson, C. G. Thelander, and C. M.White, (Eds.). Peregrine Falcon Popula-tions: Their Management and Recovery.The Peregrine Fund, Boise, Idaho, USA.

COURT, G. S., D. M. BRADLEY, C. C. GATES,AND D. A. BOAG. 1989. Turnover andrecruitment in a tundra population of Pere-grine Falcons Falco peregrinus. Ibis131:487–496. http://dx.doi.org/10.1111/j.1474-919X.1989.tb04785.x

COURT, G. S., C. C. GATES, D. A. BOAG, J. D.MACNEIL, D. M. BRADLEY, A. C. FESSER, J.R. PATTERSON, G. B. STENHOUSE, AND L. W.OLIPHANT. 1990. A toxicological assess-ment of Peregrine Falcons, Falco peregri-nus tundrius, breeding in the KeewatinDistrict of the Northwest Territories,Canada. Canadian Field-Naturalist104:255–272.

FYFE, R.W., S. A. TEMPLE, AND T. J.CADE.1976. The 1975 North American Peregrinesurvey. Canadian Field-Naturalist 90:228–273.

HENNY, C. J., W. S. SEEGAR, AND T. L. MAECH-TLE. 1996. DDE decreases in plasma of

spring migrant Peregrine Falcons, 1978–94. Journal of Wildlife Management60:342–349.

HENNY, C. J., M. A. YATES, AND W. S, SEEGAR.2009. Dramatic declines of DDE and otherorganochlorines in spring migrant Pere-grine Falcons from Padre Island, Texas,1978–2004. Journal of Raptor Research43:37–42.

HICKEY, J. J. 1969. Peregrine Falcon Popula-tions: Their Biology and Decline. Univer-sity of Wisconsin Press, Madison,Wisconsin, USA.

JARMAN, W. M., S. A. BURNS, W. G. MATTOX,AND W. S. SEEGAR. 1994. Organochlorinecompounds in the plasma of Peregrine Fal-cons and Gyrfalcons nesting in Greenland.Arctic 47:334–340.

JOHNSTONE, R. M., G. S. COURT, A. C. FESSER,D. M. BRADLEY, L. W. OLIPHANT, AND J. D.MACNEIL. 1996. Long-term trends andsources of organochlorine contamination inCanadian tundra Peregrine Falcons, Falcoperegrinus tundrius. Environmental Pollu-tion 93:109–120. http://dx.doi.org/10.1016/0269-7491(96)00037-1

KIFF, L. F. 1988. Changes in the status of thePeregrine in North America: An overview.Pages 123–129 in T. J. Cade, J. H. Ender-son, C. G. Thelander, and C. M. White(Eds.). Peregrine Falcon Populations: TheirManagement and Recovery. The PeregrineFund, Boise, Idaho, USA.

NISBET, I. C. T. 1988. The relative importanceof DDE and dieldrin in the decline of Pere-grine Falcon populations. Pages 351–375in T. J. Cade, J. H. Enderson, C. G. The-lander, and C. M. White (Eds.). PeregrineFalcon Populations: Their Managementand Recovery. The Peregrine Fund, Boise,Idaho, USA.

PEAKALL, D. B. 1976. The Peregrine Falcon(Falco peregrinus) and pesticides. Cana-dian Field-Naturalist 90:301–307.

PEAKALL, D. B., AND L. F. KIFF. 1988. DDEcontamination in Peregrines and AmericanKestrels and its effect on reproduction.Pages 337–350 in T. J. Cade, J. H. Ender-

320

– FRANKE ET AL. –

son, C. G. Thelander, and C. M. White(Eds.). Peregrine Falcon Populations: TheirManagement and Recovery. The PeregrineFund, Boise, Idaho, USA.

PEAKALL, D. B., D. G. NOBLE, J. E. ELLIOT, J.D. SOMERS, AND G. ERICKSON. 1990. Envi-ronmental contaminants in Canadian Pere-grine Falcons, Falco peregrinus: Atoxicological assessment. Canadian Field-Naturalist 104:244–254.

RALOFF, J. 2000. The case for DDT: What doyou do when a dreaded environmental pol-lutant saves lives? Science News 158:12–14.

RATCLIFFE, D. 1993. The Peregrine Falcon. T.& A. D. Poyser, London, UK.

RISEBROUGH, R. W., AND D. B. PEAKALL. 1988.The relative importance of the severalorganochlorines in the decline of PeregrineFalcon populations. Pages 449–462 in T. J.Cade, J. H. Enderson, C. G. Thelander, andC. M. White (Eds.). Peregrine Falcon Pop-ulations: Their Management and Recovery.The Peregrine Fund, Boise, Idaho, USA.

ROWELL, P., G. L. HOLROYD, AND U. BANASCH.2003. The 2000 Canadian Peregrine Falconsurvey. Journal of Raptor Research 37:98–116.

SAS INSTITUTE. 2004. SAS/STAT 9.1 User’sGuide. SAS Publishing, Cary, North Car-olina, USA.

US EPA (UNITED STATES ENVIRONMENTAL PRO-TECTION AGENCY). 2007a. Method 8081B:Organochloride pesticides by gas chro-matography.http://www.epa.gov/waste/hazard/testmeth-ods/sw846/pdfs/8081b.pdf

US EPA (UNITED STATES ENVIRONMENTAL PRO-TECTION AGENCY). 2007b. Method 8082A:Polychlorinated biphenyls (PCBs) by gaschromatography.http://www.epa.gov/waste/hazard/testmeth-ods/sw846/pdfs/8082a.pdf

VORKAMP, K., M. THOMSEN, S. MØLLER, K.FALK, AND P. B. SØRENSON. 2009. Persistentorganochlorine compounds in PeregrineFalcon (Falco peregrinus) eggs from SouthGreenland: Levels and temporal changesbetween 1986 and 2003. EnvironmentInternational 35:336–341. doi:10.1016/j.envint. 2008.08.008

WON, H., AND R. TURLE. 1987. Methods ofanalysis. Canadian Wildlife Service ReportSeries 87-00. Canadian Wildlife Service,National Wildlife Research Centre, Ottawa,Canada.

321

– REPRODUCTIVE SUCCESS OF PEREGRINE FALCONS –

322

– FRANKE ET AL. –